The majority of sick dairy cows that require treatment by farm staff or veterinary practitioners are seen during early lactation, and are typically labelled as ‘transition cow health problems’. Milk fevers, retained fetal membranes, metritis, displaced abomasum, ketosis and mastitis are all conditions that classically occur at this critical time, and it is widely acknowledged that the transition period (defined as the period from 3 weeks pre-calving to 3 weeks after calving) is a high-risk time in the production cycle of the cow. What happens during this critical period can have long-term implications for cow health, longevity, productivity and future fertility.